JPS58224440A - Manufacture of magnetic disk - Google Patents

Abstract

PURPOSE:To obtain a disk generating very little noise, by kneading a liq. reinforcer contg. fine alumina particles as a film reinforcing material with acrylic resin while grinding in a ball mill using zirconia balls, further kneading the kneaded material with magnetic iron oxide powder and a synthetic resin as a binder, and spin-coating the resulting coating material. CONSTITUTION:Fine particles of alpha-alumina obtd. by calcination at a high temp. are kneaded with acrylic resin in toluene, xylene or cellosolve acetate in a ball mill using zirconia balls having slightly lower hardness than the alumina to prepare a liq. reinforcer contg. fine particles of alpha-alumina having <=1mum size. The liq. reinforcer is added to a liq. composition contg. gamma-Fe2O3 (magnetic powder), a binding resin such as acrylic resin, epoxy resin or phenol resin, and toluene, cellosolve acetate or benzyl alcohol, and they are kneaded in a ball mill using plastic balls of nylon or ''Teflon''. The resulting magnetic coating liq. is coated on a substrate for a magnetic disk and dried to obtain a magnetic disk reducing extremely the generation of noise due to the presence of coarse alumina particles.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method of manufacturing a magnetic disk in which noise generation is suppressed.

(b) Background of the technology A magnetic disk has a substrate made of a disc-shaped aluminum alloy with a thickness of about 2 mm, on which a thin film (hereinafter referred to as magnetic film) made of a magnetic recording medium with a thickness of less than 1 μm is formed. There are
Information is recorded and reproduced from a large number of concentric tracks from a ship by holding the entire magnetic head with a small gap between the magnetic film and the magnetic disk while the magnetic disk is rotating at high speed.

This is γ-F6 as a magnetic recording medium! Oxides such as ol (iron oxide) or alloys such as N1-Co-P, Kkeru-cobalt-phosphorus) and NiCo-Cr (=+partochrome) are used. Regarding γ-Fe2O3, as a method of manufacturing a magnetic film, a method is mainly used in which the magnetic powder is mixed with a binder and the mixture is spin-coded onto a disk-shaped substrate.

On the other hand, in the case of alloys such as -Ni-Co-P and Ni-Co, thin films are formed by methods such as vacuum evaporation, plating, and sputtering.

The present invention relates to a method of manufacturing a magnetic disk in which an oxide-based magnetic film is formed by a spin code method.

(c) Conventional technology and problems r-Fe20 used as an oxide-based magnetic recording medium
1 is a needle-shaped crystal, and magnetic paint is made by mixing this with a resin binder such as epoxy resin or acrylic resin in a ball mill using a solvent such as toluene or xylene, and then A magnetic film with a thickness of less than 1 .mu.m is produced by spin-coding a thin coating made of an aluminum alloy on a thin substrate.

When the magnetic disk is rotating at high speed, the magnetic head that writes information to and reads information from the magnetic disk (
This is the buoyancy force (the state where it is 02 to 0.5 μm higher than the
As a result, there should be no sliding between the two during operation, but if dust or recording powder particles accumulate on the magnetic head, head clarity, or falling of the magnetic head, may occur, and contact start may occur. - In a magnetic disk drive having a stop configuration (C8S), since the magnetic head is in contact with the magnetic disk even after the start of rotation, there is some friction, and there is also an impact due to the jumping of the magnetic head. In this way, contact between the head and the magnetic disk is unavoidable, so it is necessary to strengthen the strength of the magnetic film by some method, such as applying a lubricant or using hard non-magnetic particles such as alumina particles. All additions are being made.

Here, the alumina particles are fired at high temperatures to form α-alumina (
corundum) and (7), and it is difficult to produce alumina fine particles with a particle size of 1 [μm] or less and a constant particle size distribution because fusion between the fine particles occurs during high-temperature firing. be.

In addition, the alumina fine particles added to the magnetic paint must be uniformly dispersed in the spin-coded magnetic film, and poor dispersion, along with the presence of coarse particles, can cause noise when reading information. known to cause an increase in

Therefore, to improve the dispersibility, it is sufficient to knead well using a normal ball mill.
Fa! 01 is needle-like crystals, and their collisions with each other or with fine alumina particles cause property deterioration, so it is not appropriate to knead for a long time.

As mentioned above, it is clear that the cause of noise in magnetic disks using oxide-based magnetic recording media is the coarse particles of the coating reinforcement added to increase hardness and the non-uniform distribution of such reinforcement. However, I couldn't find a way to resolve this.

(dl) Object of the Invention The entire purpose of the present invention is to provide a method for manufacturing a magnetic disk using an oxide-based magnetic recording medium with excellent coating film strength and low noise.

(e) Structure of the Invention The purpose of the present invention is to crush and knead a reinforcing agent liquid containing fine alumina particles as a coating film reinforcing material in a ball mill using zirconia balls, and then knead iron oxide magnetic powder and resin to form a paint. This can be achieved by a manufacturing method of spin-coding this paint.

(f) Embodiments of the Invention The inventors have discovered that the cause of noise generation in magnetic disks is due to fine alumina particles added to the magnetic paint as a coating film reinforcing agent and their non-uniform distribution ζ, and that the alumina balls in the balls 4- I found out that the n column piece 1 is all over.

That is, in a normal ball mill, alumina balls are used, and the alumina balls are crushed and mixed by collision between the alumina balls and the object or by collision between the objects.

However, when a magnetic paint containing fine particles of α-aluminum is kneaded using a ball mill, the hardness of α-alumina is so high that the fine particles of α-alumina are crushed, and collisions between the alumina balls occur. Alternatively, the alumina balls are worn out during collision with α-alumina fine particles, and at this time the particle size l
[It was found that α-alumina pieces with a size of 9 μm or more were produced, and this was the cause of noise generation.

Therefore, in the present invention, the process of dispersing α-alumina fine particles in a magnetic paint is divided into two parts: a process of dispersing α-alumina particles in a binder, and a process of making a magnetic paint. By using a full base of acrylic resin with excellent properties and using zirconia balls with a smaller hardness in place of alumina balls, the generation of alumina fine particles with a particle size of I [μm] or more can be completely prevented, and in the latter case, nylon or is kneaded using a plastic ball made of Teflon.
This prevents the characteristic deterioration of r-Fe20g due to this.

Note that oxides such as alumina have a moisture adsorption layer km on the surface.
It is known that this moisture improves the dispersibility of acrylic resins having -COOH groups in their molecules. 1, α-alumina has a hardness of 9'1: ζ, whereas zirconia has a hardness of 7, so collisions between the balls or with α-alumina particles cause the zirconia balls to wear out and produce particles. It will not be crushed during kneading and become a source of noise.

On the other hand, plastic balls are soft and are suitable for kneading materials containing acicular materials such as γ-Fe2O3, although they only knead and do not have a crushing effect.

Examples of the reinforcing agent liquid and paint will be explained below.

Acrylic resin (Mitsubishi Remin Duraclone, 5E54
37) Add 200 [g] of α-alumina fine particles to 200-[g] ζ and place in a 5-t ball mill bot.Toluene 600 Cg], xylene 235 [g), and cellosolve acetate 100 as solvents. [g] Add gold and add 4k zirconia balls with diameter 13 (I:)
A reinforcing agent solution was prepared by α-forming at 50 (rpm) for 2 days with the addition of g.

The composition of the reinforcing agent liquid is not limited to the above conditions, the weight ratio of resin to alumina is 0.5 to 3, the non-volatile fraction is 20 to 40%, and the acrylic resin content is 85 to 85% of the resin.
It may be within the range of 100%.

Next, the reinforcing agent solution made in this way is then treated with r-Feto.
Then, the resin and solvent are kneaded in a ball mill equipped with plastic balls to form a paint.

Table 1 shows the compositions of the present invention (this example), and Table 2 shows the conventional compositions in which the magnetic powder and the alumina content and resin composition are equal.

7-Table 1 Table 2-8~ The content of aluminum in the reinforcing agent liquid is preferably 3 to 25% by weight, particularly 5 to 15% by weight based on γ-Fe2O3.

The quality of the magnetic film obtained by spin-coding such a paint can be judged by the level of noise, but in this example, the noise was approximately -a5 [db] in the conventional method. In the case of the method of the present invention, it was possible to reduce it to -39 (db).

(g) Effects of the Invention By implementing the present invention, it was possible to suppress the occurrence of noise caused by the coating film reinforcement material to a minimum level.

Claims (1)

[Claims] In a magnetic disk in which a recording medium layer is formed by spin-coding iron oxide magnetic powder onto a disk substrate using a synthetic resin containing a coating film reinforcing material as a binder, a reinforcing agent liquid with alumina fine particles as an entire coating reinforcing material is used. A method for manufacturing a magnetic disk, which comprises pulverizing and kneading together with acrylic resin in a ball mill using zirconia balls, then kneading with iron oxide magnetic powder and synthetic resin to form a paint, and completely spin-coding the paint to give a 7 il-% characteristic.